A. Field of the Invention
This invention relates generally to a word processing system and more particularly to a word processing system having a horizontal and vertical scrolling.
B. Background Art
Conventional word processing systems have in the past used a memory in combination with a character generator to generate the raster lines which are provided on a display monitor for displaying characters and character modifiers known as attributes. Such attributes are, for example, an underline, a double underline, or a strike-through. Systems have also been provided which allow the use of horizontal and scrolling techniques. Horizontal scrolling permits the movement of characters horizontally on the display monitor, thus allowing the viewing of a document having a wide format. Similarly, vertical scrolling permits the movement of character lines vertically on the display monitor, thus allowing the viewing of a document having a long format. The technique of windowing has also been known. In windowing the display is divided horizontally, for example, into two windows for the viewing of portions of secondary documents in addition to the one being worked on.
Conventional word processing systems have, however, left much to be desired. The manner in which these systems provide scrolling, either vertically or horizontally, has many drawbacks in flexibility and control. For example, varying the rate of scrolling has been difficult; scrolling a portion of the lines on the display monitor without affecting the remaining portion has been limited. Further, prior systems have not been able to vertically fold a document on the display, freezing the portion of the document to the left of the fold and then horizontally scrolling the right portion. Creating windows on the display monitor and scrolling the lines in one window without affecting the other windows has had many drawbacks. More importantly, conventional word processing systems have not provided scrolling capability in a simple and flexible manner wherein the characters or raster lines appear to smoothly move across the display monitor screen.
An object of this invention is to provide soft scrolling in a simple and flexible manner in which the characters or raster lines appear to smoothly move across the screen.
Another object of this invention is to provide a soft scrolling capability wherein the scrolling rate may easily be controlled.